This Comparative International Accounting History study examines the adoption and institutionalization of double entry bookkeeping at the Royal Treasury, Portugal, and the subsequent diffusion of accounting technology to the Portuguese colonies, under the leadership of the Marquis of Pombal. The Royal Treasury was the first central government organization in Portugal to adopt double entry bookkeeping, a crucial first step in the institutionalisation of the technique within Country and Empire. The analysis of this accounting change is situated in the context of similar reforms in other European countries. The study identifies key pressures exerted over and by the Royal Treasury which resulted in the adoption of specific accounting practices and confirms that State actors are more likely to employ coercion in pursuing their ends. It provides further evidence the State as an important agent in the process of institutionalization of accounting practices. It highlights the importance of individual actors who, as powerful change agents, made key decisions that influenced the institutionalization of accounting practices.